The aim of this study is to develop equations governing left ventricular pressure and volume during a cardiac cycle. It is assumed that the stress in the myocardium is composed of an isotropic tissue pressure term and fiber tension. Fiber tension T depend on the stretching and rate of stretching of cardiac fibers as well as an internal variable c that describes the degree of electrochemical activation of the muscle fiber. Using mechanical equations of equilibrium and the constitutive equations mentioned above, a time dependent pressure-volume relation is obtained for the left ventricle. Hydraulic characteristics of the large arteries are modelled by a three parameter windkessel model. It is assumed that the aortic pressure is equal to the ventricular pressure P when the aortic valve is open. Mechanical events of the cardiac cycle are considered by using the developed model. Functional relationships are explored among the parameters identifying the contractility of the left ventricle, the resistance and compliance of the vascular system, and the experimentally observed quantities such as pressure, flow rate, etc.